Im8

Im8 is the immunity protein produced by E. coli alongside Colicin E8 to protect itself against Colicin E8's DNase Activity, by binding to the enzymatic C domain and inhibiting its activity. This occurs to prevent the cell that produces the colicin from being killed. Im8 is later released when the Colicin binds to BtuB, the outer membrane receptor on the target cell.

3D structures of colicin-E8 immunitiy protein
Colicin Immunity Protein